The invention first relates to an apparatus for the preparation of a foam spray-dried product at least comprising a housing and a nozzle situated therein, in which the nozzle connects to a conduit for supplying liquid comprising at least one of the ingredients of the end product and a supply of pressurized gas being connected to said conduit and means are provided to feed a stream of gas comprising a dry particulate material to the jet of droplets issued by the nozzle concerned.
Such an apparatus is known from U.S. Pat. No. 3,615,723. In said publication a spray drying apparatus is described in which to facilitate the drying operation and to reduce the density of the finished product the liquid which is fed to the nozzle may be supplied with air or any suitable gas. The thus formed droplets expand under influence of the gas present and are subsequently brought into contact with a dry particulate material in order to form agglomerates between the still moist expanded droplets and the dry particular material.
The axis of the jet of moist expanded droplets and the jet of dry particulate material are substantially perpendicular to each other. The agglomerated dried product obtained in this way will show non-uniform properties which is undesirable.
The present invention has an object to provide an apparatus of the above indicated type with which it is possible to prepare a very uniform product.
A further object of the present invention is to provide an apparatus with which a uniform product may be prepared which additionally enables to prepare a product of any desired bulk density.